State composition with mapState

state.js

import { mapState } from '@stated-library/core';

const todoLib = createTodoLib();
const counterLib = createCounter();

const appState$ = mapState(
  [todoLib.state$, counterLib.state$],
  ([todoLibState, counterLibState]) => ({
    todos: todoLibState.todos,
    counter: counterLibState,
    total: counterLibState + todoLibState.todos.length,
  });
);